1. Field of the Invention
The present invention relates to a method for making ceramic spheres, and more particularly to a method for making ceramic spheres wherein a ceramic sphere is made out of a cylinder-shaped core machined by a core drill.
2. Description of the Background Art
In recent years, researches on applications of ceramic materials have been vigorously performed because of excellent characteristics of ceramic material with high resistance against abrasion, heat and acid. The ceramic materials are used in various kinds of rolling-mechanical part.
For instance, ceramic ball bearing not only demonstrates no occurrence of seizure, even when the supply of lubricant stops in the middle of its operation, but also has higher resistance against abrasion when compared with the metallic ball bearings.
Silicon-nitride compounds, silicon-carbide compounds, alumina compounds or titanium nitride compounds materials are mainly used in conventional ceramic materials to make ceramic ball bearings. There are many kinds of method for making ball bearings using ceramic materials. For example, the balls of the ball bearing can be manufactured by adding binder to ceramic powder to form a spherical shape and by sintering it.
However, it is difficult to get balls of high degree of spherical shape and good precision according to the above-mentioned method. Also, it is actually impossible to manufacture these balls by press forming at high temperatures. Therefore, balls with a good degree of spherical shape, dimensions, precision, resistance against abrasion and good mechanical hardness can not be manufactured by the above-mentioned method.
As a result, a grinding technology is adopted as an alternative method for making ceramic spheres. For example, in the grinding technology, a sphere can be made by constantly cutting the edges of a cube. However, since a sphere is approximately formed according to this prior art, there is a problem that a lot of time, special jigs and skilled persons are required.
On the other hand, the improved prior art is disclosed in Korean Patent Laid-open Publication No. 1987-268. In the prior art of grinding technology, a cylinder-shaped grinding grindstone in which several arc-shaped grooves are formed on the grind-surface and cylinder-shaped rowing grindstone are disposed in an approximate parallel. A blade is disposed between a grinding grindstone and a rowing grindstone. The blade has an inclined surface toward the rowing grinding grindstone.
However, in the abovementioned prior art, there is a disadvantage in that the original shape of grindstone can not be maintained due to abrasion. Consequently, the size of ceramic sphere becomes inconsistent as time passes. Therefore, the grinding grindstone should be changed frequently to maintain the sizes of ceramic spheres uniform. In addition, since the ceramic sphere is made out of a cylinder-shaped bar, the size of the ceramic sphere is limited.